Datasheet

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LTC1821

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATIO

16-Bit, Ultra Precise,

Fast Settling V

OUT

DAC

The LTC

1821 is a parallel input 16-bit multiplying voltage

output DAC that operates from analog supply voltages of

±5V up to ±15V. INL and DNL are accurate to 1LSB over the

industrial temperature range in both unipolar 0V to 10V and

bipolar ±10V modes. Precise 16-bit bipolar ±10V outputs are

achieved with on-chip 4-quadrant multiplication resistors.

The LTC1821 is available in a 36-lead SSOP package and is

specified over the industrial temperature range.

The device includes an internal deglitcher circuit that reduces

the glitch impulse to less than 2nV•s (typ). The LTC1821

settles to 1LBS in 2µs with a full-scale 10V step. The

combination of fast, precise settling and ultra low glitch make

the LTC1821 ideal for precision industrial control applica-

tions.

The asynchronous CLR pin resets the LTC1821 to zero scale

and resets the LTC1821-1 to midscale.

■

Process Control and Industrial Automation

■

Precision Instrumentation

■

Direct Digital Waveform Generation

■

Software-Controlled Gain Adjustment

■

Automatic Test Equipment

, LTC and LT are registered trademarks of Linear Technology Corporation.

LTC1821/LTC1821-1

Integral Nonlinearity

16-Bit, 4-Quadrant Multiplying DAC with a

Minimum of External Components

DIGITAL INPUT CODE

INTEGRAL NONLINEARITY (LSB)

1.0

0.8

0.6

0.4

0.2

–0.2

–0.4

–0.6

–0.8

–1.0

16384

32768

1821 TA02

49152

65535

REF

= 10V

OUT

= ±10V BIPOLAR

LTC1821-1

OUT

OFS

10 9

24 23

15pF

17 16

–

COM

REF

12 14

0.1µF

122

OUT

15pF

OUT

1821 TA01

DGNDNC AGNDSAGNDF

–

1468

3 TO 6,

25 TO 36

CLR

16-BIT DAC

DATA

INPUTS

0.1µF

15V

–15V

0.1µF

–

DNC*

*DO NOT CONNECT

DNC*

REF

–V

REF

–V

REF

■

2µs Settling to 0.0015% for 10V Step

■

1LSB Max DNL and INL Over Industrial

Temperature Range

■

On-Chip 4-Quadrant Resistors Allow Precise 0V to

10V, 0V to –10V or ±10V Outputs

■

Low Glitch Impulse: 2nV•s

■

Low Noise: 13nV/√Hz

■

36-Lead SSOP Package

■

Power-On Reset

■

Asynchronous Clear Pin

LTC1821: Reset to Zero Scale

LTC1821-1: Reset to Midscale

Summary of content (16 pages)

PAGE 1
LTC1821 16-Bit, Ultra Precise, Fast Settling VOUT DAC U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1821 is a parallel input 16-bit multiplying voltage output DAC that operates from analog supply voltages of ±5V up to ±15V. INL and DNL are accurate to 1LSB over the industrial temperature range in both unipolar 0V to 10V and bipolar ±10V modes. Precise 16-bit bipolar ±10V outputs are achieved with on-chip 4-quadrant multiplication resistors.
PAGE 2
LTC1821 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART NUMBER TOP VIEW VCC to AGNDF, AGNDS ............................... – 0.3V to 7V VCC to DGND .............................................. – 0.3V to 7V Total Supply Voltage (V+ to V–) ............................... 36V AGNDF, AGNDS to DGND ............................. VCC + 0.3V DGND to AGNDF, AGNDS ............................. VCC + 0.3V REF, RCOM to AGNDF, AGNDS, DGND ..................
PAGE 3
LTC1821 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = TMIN to TMAX, V + = 15V, V – = – 15V, VCC = 5V, VREF = 10V, AGNDF = AGNDS = DGND = 0V. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Reference Input RREF DAC Input Resistance (Unipolar) (Note 6) ● 4.
PAGE 4
LTC1821 ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: ±1LSB = ±0.0015% of full scale = ±15.3ppm of full scale. Note 3: Using internal feedback resistor. Note 4: Guaranteed by design, not subject to test. Note 5: IOUT with DAC register loaded to all 0s. Note 6: Typical temperature coefficient is 100ppm/°C. Note 7: Measured in unipolar mode. Note 8: To 0.
PAGE 5
LTC1821 U W TYPICAL PERFOR A CE CHARACTERISTICS Logic Threshold vs VCC Supply Voltage Integral Nonlinearity (INL) INTEGRAL NONLINEARITY (LSB) LOGIC THRESHOLD (V) 2.5 2.0 1.5 1.0 0.5 Differential Nonlinearity (DNL) 1.0 1.0 0.8 0.8 DIFFERENTIAL NONLINEARITY (LSB) 3.0 0.6 0.4 0.2 0 – 0.2 – 0.4 – 0.6 – 0.8 0 1 5 2 3 4 SUPPLY VOLTAGE (V) 6 – 0.4 – 0.6 – 0.8 –1.0 0 7 49152 32768 16384 DIGITAL INPUT CODE 0.2 0 – 0.2 – 0.4 – 0.6 1.0 1.0 0.8 0.8 0.6 0.4 0.2 0 – 0.2 – 0.4 – 0.6 – 0.8 – 0.
PAGE 6
LTC1821 U W TYPICAL PERFOR A CE CHARACTERISTICS Differential Nonlinearity vs VCC Supply Voltage in Bipolar Mode 1.0 1.0 0.8 0.8 DIFFERENTIAL NONLINEARITY (LSB) DIFFERENTIAL NONLINEARITY (LSB) Differential Nonlinearity vs VCC Supply Voltage in Unipolar Mode 0.6 0.4 VREF = 10V VREF = 2.5V 0.2 0 – 0.2 VREF = 10V VREF = 2.5V – 0.4 – 0.6 – 0.8 –1.0 2 3 0.2 VREF = 10V 0 VREF = 2.5V VREF = 10V – 0.2 VREF = 2.5V – 0.4 – 0.6 – 0.8 –1.0 7 4 5 6 SUPPLY VOLTAGE (V) 0.6 0.
PAGE 7
LTC1821 U U U PIN FUNCTIONS DGND (Pin 1): Digital Ground. Connect to analog ground. VCC (Pin 2): Positive Supply Input. 4.5V ≤ VCC ≥ 5.5V. Requires a bypass capacitor to ground. D3 (Pin 3): Digital Input Data Bit 3. D2 (Pin 4): Digital Input Data Bit 2. D1 (Pin 5): Digital Input Data Bit 1. D0 (Pin 6): LSB or Digital Input Data Bit 0. CLR (Pin 7): Digital Clear Control Function for the DAC.
PAGE 8
LTC1821 TRUTH TABLE Table 1 CONTROL INPUTS CLR WR LD REGISTER OPERATION 0 X X Reset Input and DAC Register to All 0s for LTC1821 and Midscale for LTC1821-1 (Asynchronous Operation) 1 0 0 Write Input Register with All 16 Data Bits 1 1 1 Load DAC Register with the Contents of the Input Register 1 0 1 1 Input and DAC Register Are Transparent CLK = LD and WR Tied Together.
PAGE 9
LTC1821 WU W TI I G DIAGRA tWR WR DATA tDS tDH tLWD LD tLD tCLR CLR 1821 TD U W U U APPLICATIONS INFORMATION Description The LTC1821 is a 16-bit voltage output DAC with a full parallel 16-bit digital interface. The device can operate from 5V and ±15 supplies and provides both unipolar 0V to – 10V or 0V to 10V and bipolar ±10V output ranges from a 10V or –10V reference input. Additionally, the power supplies for the LTC1821 can go as low as 4.5V and ±4.5V. In this case for a 2.5V or – 2.
PAGE 10
LTC1821 U U W U APPLICATIONS INFORMATION versatility of the interface also allows the use of the input and DAC registers in a master slave or edge-triggered configuration. This mode of operation occurs when WR and LD are tied together. The asynchronous clear pin resets the LTC1821 to zero scale and the LTC1821-1 to midscale. CLR resets both the input and DAC registers. These devices also have a power-on reset. Table 1 shows the truth table for the LTC1821.
PAGE 11
LTC1821 U U W U APPLICATIONS INFORMATION Bipolar Mode (4-Quadrant Multiplying, VOUT = – VREF to VREF) operation can be achieved with a minimum of external components—a capacitor and a single op amp, as shown in Figure 2. With a fixed 10V reference, the circuit shown gives a precision bipolar – 10V to 10V output swing. The LTC1821 contains on chip all the 4-quadrant resistors necessary for bipolar operation. 4-quadrant multiplying VREF 3 2 + – 5V LT1001 0.
PAGE 12
LTC1821 U W U U APPLICATIONS INFORMATION Precision Voltage Reference Considerations Because of the extremely high accuracy of the 16-bit LTC1821, careful thought should be given to the selection of a precision voltage reference. As shown in the section describing the basic operation of the LTC1821, the output voltage of the DAC circuit is directly affected by the voltage reference; thus, any voltage reference error will appear as a DAC output voltage error.
PAGE 13
LTC1821 U U W U APPLICATIONS INFORMATION 5V LT1236A-10 9 10 R1 8 REF RCOM 2 VCC 11 12 14 ROFS RFB IOUT V + 15 R1 16 DATA INPUTS ROFS R2 LTC1821 RFB – 13 16-BIT DAC VOUT + 25 TO 36, 3 TO 6 V – 20 AGNDS LD WR 24 23 CLR DNC* DNC* DNC* 7 18 19 NC 22 21 DGND 19 VOUT = 0V TO –10V –15V 16 0.1µF AGNDF 17 *DO NOT CONNECT 6 2 LT1001 ERA82.004 3 ALTERNATE AMPLIFIER FOR OPTIMUM SETTLING TIME PERFORMANCE AGNDS AGNDF 16 200Ω 17 – 6 ERA82.
PAGE 14
LTC1821 U TYPICAL APPLICATION 17-Bit Sign Magnitude Output Voltage DAC with Bipolar Zero Error of 140µV (0.92LSB at 17 Bits) 16 15 14 LTC203AC 15V 2 1 2 3 0.1µF LT1236A-10 4 V+ 6 3 2 + – 5V 6 LT1468 0.1µF 0.1µF V– 15pF SIGN BIT 10 9 R1 RCOM 22pF 8 REF 2 11 VCC ROFS 12 14 RFB IOUT V+ R1 ROFS R2 16 DATA INPUTS RFB 13 + WR 14 24 LD 23 CLR DNC* DNC* DNC* NC 7 18 19 21 22 DGND 1 AGNDF AGNDS 17 16 VOUT VOUT V– 25 TO 36, 3 TO 6 WR LD CLR 15V 0.
PAGE 15
LTC1821 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. GW Package 36-Lead Plastic SSOP (Wide 0.300) (LTC DWG # 05-08-1642) 15.290 – 15.544* (0.602 – 0.612) 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 10.160 – 10.414 (0.400 – 0.410) 7.417 – 7.595** (0.292 – 0.299) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 2.286 – 2.387 (0.090 – 0.094) 2.463 – 2.641 (0.097 – 0.104) 0.254 – 0.406 × 45° (0.010 – 0.016) 0° – 8° TYP 0.231 – 0.3175 (0.0091 – 0.0125) 0.
PAGE 16
LTC1821 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS ADCs Low Power 400ksps, 14-Bit ADC 20mW, Single or ±5V, Serial I/O DACs Op Amps LTC1417 LTC1418 14-Bit, 200ksps, Single 5V ADC 15mW, Serial/Parallel ±10V LTC1604/LTC1608 16-Bit, 333ksps/500ksps, ±5V ADC 90dB SINAD, 100dB THD, ±2.